Human groups are in general somewhat obsessive in defining boundaries between themselves and others. Originally this stems from the genetic imperative to compete and survive and the close correlation between a group and an extended family. As the saying goes, "Four cousins, two brothers, or myself: equally valuable". Traditionally, the main boundary metrics are physical cosmetics (skin tone, body build, facial theme), belief system, residential location, and profession. In modern multicultural urban centers, speech patterns, clothing, dietary habits, and other cultural aspects such as musical taste, have also become important due to the deconstruction of traditional metrics. There is a strong tendency for immigrants to adopt a unified speech, clothing, and dietary habits while expatriates tend to keep their distinctive culture.